The proposed research will examine if a common treatment of cataract, namely, intraocular lens (IOL) insertion affects binocular functioning. Cataract removal and surgical insertion of IOLs is rapidly becoming a routine treatment of senile cataract. The success of this treatment in terms of visual functioning is usually assessed by measuring visual acuity. Yet a visual function assessment based on acuity alone ignores potential problems in binocular vision. The reason that binocular visual functioning may be disrupted is that the placement of an IOL of a given power along the optic axis is critical in achieving the correct magnification of the retinal image. If the retinal images in the two eyes have unequal magnification (aniseikonia), then normal binocular vision, especially stereopsis--the ability to judge relative depth and distances of objects and surfaces--will be disrupted. Along with a reduction of stereoacuity, aniseikonia also produces distortions of space, shapes of rooms, slant of floors, etc. Clearly an impaired ability to judge the relative depth and distances of objects coupled with a distortion of these surfaces could be very disturbing to the elderly observer. Such problems would accentuate any other sensory or motor impairment the older patient might have. There is an urgent need therefore to assess the degree of aniseikonia found following monocular cataract removal. The proposed work will assess aniseikonia and steroacuity following surgical removal of the cataractous lens in one eye. These will be measured in (1) patients with an IOL in the posterior chamber (primary implants); (2) patients with an IOL in the anterior chamber (primary or secondary implants); and (3) patients with contact lens correction. A detailed questionnaire about visual problems encountered in daily activities will be given. On the completion of this work the vision care community will be in a better position to assess changes in aniseikonia or stereopsis consequent on monocular cataract removal and the clinical significance of these changes.